Swearinger was a starter just last year wasn't he? I can see why the move was made since Green isn't someone we want to see playing defense and CGJ is in concussion protocol with Bell still being hurt.
ETA: Swearinger was only drafted in 2013 but has played for like 6 teams since. He played in four games in AZ this year - starting all 4 and playing every snap. Then he was released for some reason I haven't seen mentioned. He had a cup of coffee (one month) in Oakland this year and has been a FA since December 10.